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                括号序列再战猪猪侠                </h1>
                <p>时间限制：20s&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  空间限制：512MB</p>			</div>
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                                <h3>题目描述</h3><p><div>括号序列与猪猪侠又大战了起来。</div>
<div>众所周知，括号序列是一个只有(和)组成的序列，我们称一个括号</div>
<div>序列S合法，当且仅当:</div>
<div>1.( )是一个合法的括号序列。</div>
<div>2.若A是合法的括号序列，则(A)是合法的括号序列。</div>
<div>3.若A，B是合法的括号序列，则AB是合法的括号序列。</div>
<div>我们考虑match[i]表示从左往右数第i个左括号所对应的是第几个右</div>
<div>括号，现在他得到了一个长度为2n的括号序列，给了你m个信息，第i</div>
<div>个信息形如ai,bi，表示match[ai]&lt;match[bi]，要你还原这个序列。</div>
<div>但是你发现这个猪猪侠告诉你的信息，可能有多个括号序列合法；甚</div>
<div>至有可能告诉你一个不存在合法括号序列的信息！</div>
<div>你最近学了取模运算，你想知道答案对998244353(7*17*2^23+1)取</div>
<div>模的结果，这个模数是一个质数。</div>
<div></div>
<div></div>
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<div></div></p><hr/><h3>输入格式</h3><p><div>
<div>第一行一个正整数T,T&lt; = 5，表示数据组数。</div>
<div>对于每组数据，第一行一个n,m，n表示有几个左括号，m表示信息数。</div>
<div>接下来m行，每行两个数ai,bi，1&lt; = ai,bi&lt; = n。</div>
<div></div>
</div>
<p></p></p><hr/><h3>输出格式</h3><p><div>
<div>对于每组数据，输出一个数表示答案。</div>
<div></div>
</div>
<p></p></p><hr/><h3>样例输入</h3><pre>5
1 0
5 0
3 2
1 2
2 3
3 2
2 1
2 3
3 3
1 2
2 3
3 1
</pre><hr/><h3>样例输出</h3><pre>1
42
1
2
0</pre><hr/><h3>提示</h3><p><p>&nbsp;对于前两个点，是卡特兰数的情况。</p>
<div>对于第三个点，合法的情况只可能是 ()()()。</div>
<div>对于第四个点，合法情况可能是 (()()) 或者 (())()</div>
<div>对于第五个点，由于拓扑关系形成了环，显然无解。</div>
<div></div>
<div>对于 100% 的数据，保证 n &lt; = 300</div></p><hr/><h3>题目来源</h3><p>没有写明来源</p>
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